SCALABLE ENTERPRISE RAID

SCALABLE ENTERPRISE RAID<@VM>The range of RAID arrays extends from two to 250 drives<@VM>RAID arrays can give high throughput while protecting against loss of data






The TX8000, left, from LaCie has a single controller, eight drives and Fibre Channel and Wide Ultra2 SCSI connectivity. It's priced at $7,995. EMC's Sym-
metrix systems, right, have a rackmount design and are priced at $293,000.


These storage systems provide
safety in numbers'and quick access to boot


By J.B. Miles

Special to GCN

Since the early days of computing, information systems managers have faced the double-edged challenge of providing fast access to mission-critical data while protecting it from loss or corruption. The challenge persists, even as high-profile technologies such as storage area networks and network-attached storage come on the scene.

As a result, the market for external RAID subsystems, already healthy, will soar to nearly $25 billion by 2002, according to industry experts. A fair share of that market will include federal systems.

RAID systems combine several, sometimes hundreds, of hard disk drives into one virtual storage system. A simple tower or rackmount RAID module may contain eight or nine disk drives, but also may be daisychained to other modules to form a huge system with hundreds of drives. In all cases, the host computer recognizes only one large drive through the RAID controller or controllers inside the enclosures.

Corral that data

Think of a basic RAID system as an enclosure with eight or nine empty bays for holding disk drives. Add a power supply, cooling fans and high-speed SCSI or Fibre Channel interfaces for linking to host servers and other modular expansion units. Single or dual controllers usually come with each enclosure or expansion module to manage the drives it contains, making them appear as a single, logical drive to the host. The whole thing is run by RAID software provided by the manufacturer that tells the controllers how to behave.

The products listed in this guide allow you to expand from a fairly small subsystem to enterprise-level RAID with relative ease. A small array can be built around a tower or rackmount configuration that holds between two and eight drives for a storage capacity ranging from under 100G to 250G or more, depending on the number and capacity of the drives that are used.

By adding expansion modules to a unit, you can scale a system to 100 drives or more and create a boost in storage capacity into the 1T'1,000G'range.

A RAID array can use tape or 5.25-inch magnetic disk drives. The ones listed here use 3.5-inch magnetic drives, which are the most common today. Some units with 3G drives are still around, but most current RAID arrays have 9G or 18G drives, which double the capacity without adding much to the overall space taken up in each drive bay.

New drives with capacities of 36G and even 50G are coming on fast as well'though because the latter involve the use of more drive spindles, there is a slight performance price to pay in speed, especially in the 50G drive category. Thus, a modular RAID array with 100 18G disk drives can generate about 1.8T of storage capacity.

Most of the arrays listed can be scaled up from a handful of gigabytes to one, two or more terabytes of storage. As such, they would be appropriate for a department that requires 250G to 500G of storage with the ability to expand the system, when necessary, to serve as an enterprise or data center array with even higher storage requirements.




The NexStor 8Le and 8FL from nStor operate at a range of RAID levels,
with eight drives and single controllers.


Who's driving?

The extent to which you can scale a particular array depends on how many drives you place in your base module, the individual capacities of those drives and how many extension modules are allowed by the manufacturer.

As for price, the more storage capacity and features you want'redundant components, dual failover controllers, fast Fiber Channel interfaces'the more you'll pay.

Base models of highly scalable arrays such as Dot Hill Systems Corp.'s LR-5000/7000, Cambex Corp.'s Centurion 2000 series and Raidtec Corp.'s FibreArray series fall into the $10,000 range. But building them into high-end enterprise arrays with terabytes of storage capacity will cost $150,000 or more.

Advanced arrays loaded with hundreds of drives and 3T or 4T of storage can cost $350,000 or more. Are they worth it? If your data is mission-critical, who can put a price tag on it?

Many of the arrays listed in this guide provide full protection against data loss and high throughput speeds for a per-megabyte cost of 25 cents or less.

RAID supplies two critical benefits: 100 percent protection against data loss and speedy input/output performance. RAID works by striping portions of a file across different drives. A single file may have one segment of data on Drive 1, more data on Drive 2, and so on. The data can be recovered via parity checking'parity is a mathematical formula for storing files on disks'and mirroring, which stores the same file on several drives.

But in both cases, redundancy is key: If one drive fails, access to critical data isn't lost because it resides in various forms on other drives.




Data General's Clariion FC5700 Series features RAID levels 0, 1, 3, 5 and 0+1.


Don't turn it off

Other protections RAID systems supply are hot-swapping and fault-tolerant components. Hot-swapping replaces failed drives or controllers without powering down the system, thus saving money and aggravation by eliminating costly downtime.

Fault-tolerant RAID components include redundant power supplies, cooling systems, multiple host interfaces, dual buses and dual failover controllers, which direct the secondary controller to kick in immediately if the primary controller fails.

Adding fault-tolerant components increases the cost of a RAID system, but they also provide virtually foolproof insurance against cataclysmic system failure and data loss.

As for I/O performance boosts, RAID arrays alleviate the bottlenecks common in single-drive systems. Because RAID striping distributes segments of data files on disks throughout the array, each drive head can access the segments quickly and pass them through the system simultaneously. ''One of the best uses of RAID is for online transaction processing (OLTP), where many I/O requests compete for drive access and can bog down the server. But RAID storage is also used as a counterpart to enterprise SANs, high-speed, high-bandwidth storage networks that logically connect storage devices to ser-vers.

When researching RAID systems you'll see the term RAID levels.

Vendorspeak aside, RAID levels are descriptions of how multiple drives are connected and how they work together to protect data.

There are five common levels:

RAID 0. By itself, Level 0 amounts to almost RAID. RAID 0 distributes, or stripes, data across the array. It provides fast transfer rates, but the data isn't duplicated from disk to disk. So if one disk fails, the entire array goes down.

RAID 1. Level 1 provides disk mirroring. A simple RAID 1 system consists of two drives on which duplicate information is written simultaneously. Level 1 provides dependable, albeit basic, data reliability because of its redundancy'two disks hold the same information. But it lacks parity checking, so corrupted data on one disk could corrupt data on another.

RAID 0+1. Known as striped mirrored array, Level 0+1 blends the speed of RAID 0 with the redundancy of RAID 1 for inexpensive data protection and fast throughput.

RAID 3. Level 3 combines data striping with a dedicated parity drive for error recovery.

Three drives are required: one for parity and two for striping. This level also requires extra data overhead for parity checking, and when combined with other re-quirements makes it more expensive than RAID 0+1.

RAID 5. Level 5 stripes blocks of data and the parity checking formulas together across multiple drives, thus eliminating the need for a separate parity drive.





Tips for buyers

' Remember: The cost of any RAID array is determined by the number and capacity of the drives it holds, the number of expansion modules used and the type of redundant or fault-tolerant components required.

' Develop a five- to 10-year plan before selecting a scalable RAID system.


' Buy dual failover RAID controllers, redundant power supplies, cooling fans and host interfaces to ensure the best protection against catastrophic array failures.


' Equip your RAID array with an uninterruptible power supply.


' Decide which interface technology'SCSI, Fibre Channel or other'is suitable for your host platforms, operating system and other network components.

' Investigate your RAID manufacturer's software as well as its hardware.

' Remember'a higher number isn't better. RAID levels have no hierarchy of value.


' Buy all the RAID you can afford'you're likely to need it later.



This level is popular with users because it supports most high-end applications, including OLTP with its demanding read-write ratios. It is also dependable, but when a drive fails, recovery time is slow because the information on the failed drive must be reconstructed from the parity data on other drives.

Not so common

There are several other seldom-used RAID levels, including levels 4 and 6. Levels 10 and 53 amount to vendorspeak for RAID 0+1 and RAID 5 and 3, respectively.

A white paper from PerifiTech Inc., a RAID array manufacturer in Hinkley, Ohio, suggests that when choosing a RAID level, consider the following factors:

' The number of users and the amount of drive capacity needed

' The importance of the applications and data to the cost of downtime and lost business

' The size of the data blocks and whether they require direct or sequential access on the drives

' The ratio of reads to writes to I/O activity, and the maximum transfer rate needed

' The capabilities of the various RAID levels; a high number is not necessarily indicative of a better choice.


J.B. Miles, of Pahoa, Hawaii, writes about communications and computers.































































































































































































































































































































































































































































































































































VendorProductRaid
levels
Scalability
in drives
Controllers
per
enclosure
Host
interfaces
ConfigurationPrice
Andataco/nStor Inc.
San Diego, Calif.
619-453-9191
www.iplsys.com
GigaRAID/AA0, 1, 3, 5,0+18 to 60DualUltra SCSI,
Fibre Channel
Tower,
rackmount
$12,070
GigaRAID/SX0, 1, 3, 5, 0+18 to 16Single or
dual
Ultra SCSI,
Fibre Channel
Tower,
rackmount
$11,900
GigaRAID/FT0, 1, 0/1, 3, 57 to 30Single or
dual
Fibre ChannelDesktop,
rackmount
$16,095
GigaRAID/FC0, 1, 0/1, 3, 57 to 30Single or
dual
Fibre ChannelTower,
rackmount
$14,890
Cambex Corp.
Waltham, Mass.
781-890-6000
www.cambex.com
Centurion
2000
M/FM
0, 1, 3, 5, 0+110 to 50DualUltra SCSI,
Fast Wide
SCSI, Fibre
Channel
Rackmount$10,000
Centurion
2000 FJ
0, 1, 3, 5, 0+12 to 12DualFibre ChannelRackmount$10,000
Centurion
2000 SA
0, 1, 3, 52 to 12DualIBM SSARackmount$10,000
Ciprico Inc.
Plymouth, Minn.
612-551-4000
www.ciprico.com
6500 Series39SingleUltra Wide
SCSI
Desktop,
Rackmount
$13,500
6900 Series34 to 9SingleUltra Wide
SCSI
Rackmount$13,500
7000 Series39SingleFibre ChannelRackmount$13,500
CyberneticsYorktown, Va.
757-833-9100
www.cybernetics.com
CY-RDA
Series
0, 1, 4, 5, 0+18 to 48Single or
dual
Ultra SCSITower,
rackmount
$41,095
CyberStorage Systems
Littleton, Mass.
978-486-0005
www.cyberstorage.com
Ultra 3080, 1, 3, 5, 0+17 to 84Single or
dual
Ultra SCSITower,
rackmount
$28,575
CybrFibre0, 1, 4, 5, 0+1up to 250SingleFibre ChannelRackmount$37,280
Data General Corp.
Westboro, Mass.
508-898-5000
www.dg.com
Clariion
FC5500
Series
0, 1, 3, 5, 0+1up to 120Single or
dual
Fibre ChannelDeskside,
rackmount
$67,800
Clariion
FC5700
Series
0, 1, 3, 5, 0+1up to 120Single or
dual
Fibre ChannelDeskside,
rackmount
$60,500
Clariion
3400/3500
Series
0, 1, 3, 5, 0+13 to 16Single or
dual
Fibre ChannelDeskside,
rackmount
$27,960
Dot Hill Systems Corp.
Carlsbad, Calif.
760-931-5500
www.artecon.com
LynxArray II0, 1, 3, 5, 0+13 to 17SingleUltra Wide
SCSI, Wide
Ultra2 SCSI,
Fibre Channel
Tower,
rackmount
$7,500
LR-50000, 1, 3, 5, 0+17 to 43DualUltra SCSITower,
rackmount
$13,500
LR-70000, 1, 3, 5, 0+17 to 43DualUltra SCSITower,
rackmount
$16,000
SuperFlex0, 1, 3, 5, 0+17 to 14Single or
dual
Ultra SCSITower,
rackmount
$9,500
Lynx
NSS5000
0, 1, 3, 5, 0+19 to 42SingleUltra SCSITower,
rackmount
$30,000
RAID Box
5300
Turbo+
0, 1, 3, 5, 0+12 to 120DualUltra SCSITower$8,000
ECCS Inc.
Tinton Falls, N.J.
732-747-6995
www.eccs.com
Synchronix
2000
0, 1, 3, 5, 105 to 90Single or
dual
Ultra Wide
SCSI
Rackmount$20,000
EMC Corp.
Hopkinton, Mass.
508-435-1000
www.emc.com
Symmetrix
Series
0, 1, 5, 0-14 to 120Single or
dual
Fast Wide
SCSI, Ultra
SCSI, Fibre
Channel
Rackmount$293,000
Eurologic Systems Inc.
Acton, Mass.
978-266-9224
www.eurologic.com
Voyager
5000
0, 3, 4, 5, 0+1up to 42SingleUltra SCSI,
Fast Wide
SCSI
Tower$19,995
Hewlett-Packard Co.
Palo Alto, Calif.
650-857-1501
www.hp.com
Model 30/FC0, 3, 5, 0+1up to 30DualFibre ChannelRackmount$34,080
SureStore E
Disk Array 12H
0, 3, 5, 0+112DualSCSI-2Tower,
rackmount
$6,220
Hitachi DataSystems Corp.
Santa Clara, Calif.
408-970-1000
www.hds.com
Freedom
5700E Series
0, 1, 55 to 20SingleUltra SCSI,
Fibre Channel
Tower,
rackmount
$22,850
IBM Corp.
Armonk, N.Y.
408-256-1600
www.storage.ibm.com
Fibre Channel
RAID Storage
Server
0, 1, 3, 5, 0+110 to 60DualFibre ChannelTower,
rackmount
$39,350
Integrix Inc.
Newbury Park, Calif.
805-376-1000
www.integrix.com
IQstor R15000, 1, 3, 5, 0+16Single or
dual
Ultra Wide
SCSI, Ultra2
SCSI, Fibre
Channel
Desktop,
tower,
rackmount
$13,000
IQstor R20000, 1, 3, 5, 0+16Single or
dual
SameDesktop,
tower,
rackmount
$23,000
Jems Data Inc.
Andover, Mass.
978-749-3660
www.jemsdata.com
Orbiter-LVD0, 1, 3, 5, 0+17 to 76Single or
dual
Ultra2 LVD
SCSI
Tower,
rackmount
$7,300
Orbiter-FC0, 1, 3, 5, 0+17 to 118Single or
dual
Fibre ChannelTower,
rackmount
$9,800
LaCie Ltd.
Hillsboro, Ore.
503-844-4500
www.lacie.com
TX80000, 1, 3, 5, 0+18Single or
dual
Wide Ultra2
SCSI, Fibre
Channel
Tower$7,995
Land-5 Corp.
San Diego
858-566-2514
www.land-5.com
ICEbox DS
2000
0, 1, 3, 5, 0+12 to 18SingleUltra Wide
SCSI, Ultra2
SCSI, Fibre
Channel
Rackmount$11,000
LSI Logic Inc.
Wichita, Kan.
316-636-8000
www.lsilogic.com
MetaStor
S-Class Series
0, 1, 3, 5, 0+110 to 100Single o
rdual
Wide Ultra2
SCSI
Tower,
rackmount
$9,000
Media Integration Inc.
Soquel, Calif
800-824-7385
www.mediainc.com
AssetStor
5800
0, 1, 510 to 30DualUltra Wide
SCSI, Ultra2
SCSI, Fibre
Channel
Tower,
rackmount
$49,495
MicroNetTechnology Inc.
Irvine, Calif.
949-453-6100
www.micronet.com
G4FCRAID
Series
0, 1, 3, 5, 0+17 to 28SingleFibre ChannelRackmount$94,000
G4UWRAID
Series
0, 1, 3, 5, 0+17 to 28SingleUltra Wide
SCSI
Rackmount$80,280
MTI TechnologyCorp.
Anaheim, Calif.
714-970-0300
www.mti.com
Gladiator
3600
0, 1, 5, 0+112 to 71DualFibre ChannelRackmount$57,140
Gladiator
6700
0, 1, 5, 0+112 to 120DualFibre ChannelRackmount$149,000
Gladiator
3500
0, 1, 5, 0+112DualUltra SCSIRackmount$61,050
nStor Corp.
Lake Mary, Fla.
407-829-3500
www.nstor.com
NexStor 8Le0, 1, 3, 4, 5, 0+18SingleUltra2 SCSITower,
rackmount
$8,165
NexStor 8FL0, 1, 3, 4, 5, 0+18SingleFibre ChannelTower,
rackmount
$10,499
Peripheral Technology
Group Inc.
Eden Prairie, Minn.
612-942-7474
www.ptgs.com
RAIDION.fc0, 1, 3, 5, 0+13 to 90SingleFibre ChannelTower,
rackmount
$12,000
PerifiTech Inc.
Hinckley, Ohio
330-278-2070
www.perifitech.com
Aerial Array
SCSI
Subsystem
0, 1, 3, 5, 0+18 to 35Single or
dual
Ultra SCSITower,
rackmount
$8,299
Aerial Array
u2-SCSI
0, 1, 3, 5, 0+18 to 35Single or
dual
Ultra2 SCSITower,
rackmount
$8,799
Procom Technology
Inc.
Irvine, Calif.
949-852-1000
www.procom.com
Reliant 10000, 1, 3, 5, 0+110 to 50SingleUltra Wide
SCSI, Fibre
Channel
Rackmount$28,995
Raidtec Corp.
Alpharetta, Ga.
770-664-6066
www.raidtec.com
FibreArray-120, 1, 3, 5, 0+112 to 126SingleFibre ChannelTower,
rackmount
$7,860
FibreArray HI0, 1, 3, 5, 0+17 to 110SingleFibre ChannelTower,
rackmount
$9,020
FlexArray HI0, 1, 3, 5, 0+17 to 28SingleUltra2 SCSITower,
rackmount
$6,430
Sun MicrosystemsInc.
Mountain View, Calif.
650-960-1300
www.sun.com
StorEdge
A5100
0, 1, 5, 0+12 to 14SingleFibre ChannelTower,
rackmount
$35,000
StorEdge
A5200
0, 1, 5, 0+12 to 22Dual
redundant
Fibre ChannelTower,
rackmount
$51,000
StorEdge
A3500
0, 1, 5, 0+12 to 22Dual
redundant
Ultra SCSITower,
rackmount
$51,850
StorEdge
A1000/D1000
0, 1, 5, 0+14 to 108Dual
redundant
Ultra SCSITower,
rackmount
$9,095
Storage Technology
Corp.
Louisville, Colo.
719-536-4055
www.storagetek.com
OPENstorage
916x Series
0, 1, 5, 0+110 to 20DualFibre ChannelTower,
rackmount
$39,100















































































VendorProductRaid
levels
Scalability
in drives
Controllers
per
enclosure
Host
interfaces
ConfigurationPrice
Western ScientificInc.
San Diego
619-565-6699
www.wsm.com
CycloneRAID
Ultra
3, 54 to 44SingleUltra Wide
SCSI
Tower,
rackmount
$16,860
CycloneRAID
Ultra-2
3, 54 to 44SingleUltra2 SCSITower,
rackmount
$18,830
CycloneRAID
FC
3, 54 to 44SingleFibre ChannelTower,
rackmount
$20,340
Winchester SystemsInc.
Woburn, Mass.
781-933-8500
www.winsys.com
FlashDisk
RAID
1, 3, 5, 0+14 to 72SingleUltra Wide
SCSI
Tower,
rackmount
$10,000
Xiotech Corp.
Eden Prairie, Minn.
612-828-5980
www.xiotech.com
Magnitude
Series
1, 3, 5, 0+12 to 32Single or
dual
Ultra Wide
SCSI
Tower,
rackmount
$55,000
Xyratex International
Ltd.
Irvine, Calif.
949-476-1016
www.xyratex.com
SR-1294-MYFL1, 3, 5, 0+12 to 12Single or
dual
Ultra2 SCSI,
Fibre Channel
Rackmount$8,541
SR-1201-MYFF1, 3, 5, 0+12 to 12Single or
dual
Fibre ChannelRackmount$9,639

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